Method for manufacturing a printed and embossed floor covering

ABSTRACT

An improved process is disclosed for forming tiles that are embossed in register with a printed design. A printed design is first applied to a base coat and a wear coat is laminated over the design. Advantageously, the wear coat is applied to the printed web before it is heated for lamination. Before embossing occurs, the laminated product is cooled until partial setting occurs, and the embossing roll is sprayed with water in order to minimize the likelihood that the laminated product will adhere to the embossing roll. To avoid distorting the web during lamination and embossing, proper web tension is maintained by controlling the rotational speeds of the laminating drum and the embossing roll so that a desired ratio is preserved. The web is then cut into oversized tiles that shrink to size during annealing.

This is a continuation of application Ser. No. 525,892, filed Aug. 24,1983, now abandoned.

BACKGROUND OF THE INVENTION

This invention concerns a printed and embossed material, suitable foruse as a floor covering, and a method and apparatus for making it in acontinuous process. More particularly, it concerns a multilayeredmaterial combining a base layer, a printed layer and a wear resistantlayer, which is embossed in register with the print.

Reverse printed laminates have been made by laminating separate sheetsof calendered base material and a preprinted plastic film. In continuousprocesses, the printed designs have been limited to random printsbecause of the difficulty of maintaining the desired dimensions in thepreprinted plastic film, in the laminate and in some cases in the basematerial. The plastic film tends to stretch when it is being printed andsubsequently dried. Since it is necessary to apply tension to theprinted film during lamination in order to eliminate trapped air andwrinkles, the printed design can also be distorted during lamination.

Alternatively, tiles can be formed in batch processes with designs thatare in register to the cut tile by laminating preprinted plastic sheetsof silk screen designs to sheets of a suitable base material. The tilescan then be hand clicked from the sheets. The high cost of such a batchprocess makes in-register printed tile quite expensive and limits itsacceptance.

An additional complication is imposed by the desirability of providing atextured surface by embossing the tile. Because the embossing step canbe another cause of distortion, some processes are limited to embossingof a plastic surface layer that is integral with a nonplastic stablesubstrate such as asbestos or asphalt-saturated felt.

Alternatively, as described in U.S. Pat. No. 4,312,686, which isincorporated herein by reference, the distortions which occur duringprinting and laminating are minimized by printing the design on a stablebase, preferably release paper, and then transferring the printed designto a hot plastic web made continuously by an extruder. A stress relievedhot plastic film is then laminated to the printed web to provide aprotective wear coat. To emboss in register with the printed design, thelaminated product is first aligned by means of registration marks thatare printed along with the design. Embossing is then made using aconventional engraved roll having raised sections which are images ofthe printed design. After embossing, the web is partially cooled andannealed. It is then aligned with a die cutter using the sameregistration marks as used for alignment during embossing. As a result,individual tiles are cut automatically in register to the printed andembossed pattern. Although the method described in the '686 patent isoperative, a process line using this method has been limited to webspeeds on the order of 90 feet per minute with a yield of about 50%firsts and 15% seconds with the remaining 35% scrap.

SUMMARY OF THE INVENTION

We have devised an improved process suitable for continuously producingtiles in which an embossed design is in register with the tile. Theimproved process generally follows the steps disclosed in the '686patent. In accordance with this process, the design is printed on astable base, preferably release paper, and the printed design is thentransferred to a plastic web that is made continuously. A wear coat isthen laminated onto the printed web and this laminate is embossed usinga conventional engraved roll having raised sections which are images ofthe printed design.

As in the '686 patent, distortions are minimized by supporting theplastic web on a belt which is not an integral part of the finishedproduct and alignment is performed by maneuvering the belt. Moreover, inaccordance with the invention, proper tension of the web is maintainedto avoid distorting the web during lamination and embossing. By ensuringproper tension, the laminated product does not become distorted eitherby bunching up which causes lateral expansion in the directiontransverse to the direction of travel of the web or by stretching in thedirection which is the same as the direction of travel of the web.Proper tension is preserved by continuously monitoring the rotationalspeed of the rotating drum, the embossing roll and backup roll tomaintain them at a desired speed ratio.

After embossing, the web is cooled in a water bath, is partiallyannealed and is cooled. It is then aligned with a die cutter using thesame registration marks as used for alignment during embossing. As aresult, individual tiles can be cut automatically in register to theprinted and embossed pattern. Advantageously, the tiles are cut slightlyoversize and are further annealed to shrink them to their proper size.

Preferably, the wear coat is laminated onto the printed web by using aheated rotating drum to apply a plastic film to the printed web and thenheating the film and web. To prevent the laminated web from adhering tothe embossing roll, the roll and the laminated web are cooled withsprays of water which cause the laminated web to set partially at theembossing stage.

When using this method in a process line, we have found it possible torun the web at speeds of up to 160 feet per minute and expect to achievespeeds of about 180 feet per minute. Moreover, we have been able toproduce yields of about 88% firsts and 3% seconds.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other objects, features and advantages of our invention willbe more readily apparent from the following detailed description of apreferred embodiment of the invention in which:

FIG. 1 is a block diagram illustrating the major steps followed in thepractice of our invention;

FIG. 2 is a schematic diagram of a preferred embodiment of apparatusused in the practice of our invention;

FIG. 3 is a cross-section of a base web used in the practice of ourinvention;

FIG. 4 is a cross-section of a base web after a print layer has beentransferred to it in accordance with our invention;

FIG. 5 is a cross-section of the base web after a vinyl film has beenlaminated over the print layer;

FIG. 6 is a view of an embossing roll used in the practice of ourinvention;

FIG. 7 is a cross-section of the base web, print layer and vinyl filmafter it has been embossed in register with the print by the embossingroll of FIG. 6; and

FIG. 8 is a plan view of a tile which has been embossed in register withthe print using the embossing roll of FIG. 6.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIGS. 1 and 2 illustrate a preferred method and apparatus for practicingour invention to make a solid vinyl tile on which a decorative layer ofprint has been embossed in register with the print. Substantial portionsof this method and apparatus are similar to those described in the '686patent. Cross-sectional and plan views of the finished tile are shown inFIGS. 7 and 8.

As shown in FIG. 1, the major steps followed in making such a tilecomprise: forming a continuous web of vinyl, transfer printing on thisweb, laminating a protective wear coat over the print to form acomposite, embossing the composite in register with the print, and tilecutting in register with the print. In accordance with the invention,the composite is embossed in register with the print while maintainingproper tension in the web as it is fed into the embossing roll.Preferably, the embossed laminate is partially annealed before cutting;and further annealing is performed on the tiles after they are cut.Infrared heating is used to raise the web and the wear coat toappropriate temperatures for transfer printing, laminating, andpre-annealing. Final annealing is accomplished in a hot air oven.

Specific apparatus for performing the steps of FIG. 1 is shown in FIG.2. A continuous base web of vinyl is prepared by blending itsconstituents in blenders 20 and supplying the mix to a continuous mixer22. Hot plastic from mixer 22 is continuously supplied to a calender 30comprising a pair of rolls 32, 34 which produces a continuous hotplastic base web 10 having a surface smooth enough to receive a layer ofprint. As is known in the art, a doctor knife (not shown) may be used toseparate base web 10 from the calender rolls. A cross-section of aportion of base web 10 as it leaves the calender rolls is depicted inFIG. 3. The thickness of this cross-section typically ranges from about30 to 120 mils (0.75 to 3 mm.). The width of this cross-section is about14 inches (35 cm.) Other dimensions, however, may be used in thepractice of our invention.

As described in the '686 patent, hot plastic web 10 flows continuouslyonto a moving carrier belt 40 which is made of a material such that theweb will adhere to the belt when the web is hot, but can be removed fromit when the web is cool. Typically, such a carrier belt is made of wovenfiberglass impregnated with a silicone elastomer. Carrier belt 40 movesbase web 10 through the printing, laminating and embossing stages,supporting the web during these steps. The belt is driven at this speedby a drive roll 46 that is driven by means of a conventional line shaft48. To avoid distorting the plastic web and the design printed thereon,the web is guided and aligned by adjusting the carrier belt by means ofa guidance system 42. Near calender 30, a loop speed sensor 44 is usedto control the speed of the carrier belt so that the hot plastic webleaves calender rolls 32, 34 at a constant speed.

As it is moved away from calender 30, web 10 is heated to thetemperature required to obtain transfer of print from a pre-printedrelease paper to the web. A first infrared heater 50 heats web 10directly; and a second infrared heater 52 heats carrier belt 40 which,in turn, heats web 10. For the transfer printing system used in thepractice of the preferred embodiment of our invention, this temperatureis about 250° F. (121° C.).

Next, the web enters a transfer printing station 60 that transfers alayer of print from a preprinted release paper 62 to web 10. The printlayer can form any kind of design. For high-volume commercial productionof tiles the design is preferably one that permits tiles to be cut withthe design centered in the tile so that it is in register with the edgesof the tile.

The preprinted paper is fed from a supply roll 64, through transferrolls 66, 67 to a takeup roll 69. In practicing our invention we havefound it useful to cool roll 66 to about 70° F. (21° C.) to facilitatetransfer printing. To ensure proper alignment of the printed paper in atransverse direction, an edge guidance system (not shown) is used.Moreover, to permit splicing of rolls of preprinted paper it ispreferable to use conventional splicing equipment (not shown) includingan unwind roll stand, a splice table and a compensator that allows timeto splice the printed design in register.

To transfer the layer of print from the release paper, paper 62, web 10and carrier belt 40 are fed through the nip formed by rolls 66, 67; andthe paper is then separated from the web. Advantageously a release plate(not shown) can be used at the point of separation of paper 62 from web10 and takeup roll 69 can be provided with suitable tension controldevices. A cross-section of the printed web depicting base web 10 and aprint layer 12 is shown in FIG. 4. This cross-section is not to scalebecause the thickness of the print layer is quite small (0.0025 to 0.025mm.) compared to the 0.75 to 3 mm. thickness of base web 10.

The printed web is then heated indirectly by an infrared heater 72 thatheats the underside of carrier belt 40. The web is next fed into alaminating station 80 where a web 82 of vinyl film is laminated to theprinted side of web 10 to provide a protective wear coat. Laminatingstation 80 comprises a heated rotating drum 83, an upper high intensityinfrared heater 93, a web guide 89, a supply roll 86, and rollers 87,88, 91 and 92. In addition, the station preferably includes conventionalsplicing equipment (not shown) including an unwind roll stand, a hotsplicer and a compensating device which allows time to splice the film.

Drum 83 is driven by line shaft 48 which is coupled to the drum by meansof a speed control 85 such as a Specon speed control manufactured byFairchild Hiller. As described below, the speed control 85 regulates thespeed of the drum relative to that of the embossing roll and backuproll.

Supply roll 86 provides a continuous web of pre-formed vinyl film.Typically, the vinyl film is from 3 to 12 mils (0.075 to 0.3 mm) inthickness.

Web 82 passes through web guide 89 which moves web 82 in a transversedirection so that web 82 is in register with the printed web.Illustratively, web guide 89 is a Fife edge guide. Web 82, the printedweb and carrier belt 40 pass through the nip formed by rotating drum 83and roller 91; and web 82 is pressed and laminated by drum 83 onto theprinted web. These webs adhere to carrier belt 40 and strip away fromrotating drum 83 at roller 92 and pass on carrier belt 40 under heater93. Infrared heater 93 heats the vinyl film and, therefore, the printedweb. For the films used in the practice of the preferred embodiment ofthe invention, the temperature of web 82 is raised to approximately 310°F. (154° C.) by infrared heater 93 with the result that the vinyl filmis stress relieved and forms a composite 16 in which print layer 12 islocated between webs 82 and 10. A cross-section of composite 16 showingvinyl wear coat 82 over print layer 12 is shown in FIG. 5.

The carrier belt then moves the composite to an embossing station 110.This station comprises an embossing roll 112, a rubber backup roll 113,and means for transverse and longitudinal positioning of the laminatedweb. As shown in FIG. 6, embossing roll 112 is an engraved or etchedsteel or copper roll having areas 122 that are raised above other areas123 on the roll. Typically the difference in height between areas 122and 123 averages about 6 to 14 mils (0.15 to 0.35 mm.). Preferably,areas 122 constitute an image of the design that is transfer printedonto the base web. Both the embossing roll and the backup roll are watercooled.

The positioning means includes two electric eyes 115, 116, a speedcontrol means 117 and a positioning roll 118. Backup roll 113 is drivendirectly by line shaft 48 so that its surface speed is the same as thatof drive rolls 46. Embossing roll 112 is also driven by line shaft 48but its speed is controlled by speed control means 117. The electriceyes sense registration marks which are printed on the web along withthe printed design. Electric eye 115 controls positioning roll 118 whichguides composite 16 in the transverse direction so that the embossingroll areas 122 are in register with the images on the printed web.Electric eye 116 is connected to speed control 117 and controls thephase of the embossing roll so that embossing roll areas 122 are inregister in the longitudinal direction with the printed pattern on theweb. Specific apparatus for producing transverse and longitudinalregistration with the embossing roll include a Fife photoelectric linecontrol and a Bobst Champlain registron control, respectively. Numerousother devices will be apparent to those skilled in the art.

The outer surface of embossing roll 112 is cooled directly by a waterspray 119, and this spray also cools the upper surface of composite 16.Water spray 119 cools and sets composite 16 to such a degree thatstretching of composite 16 by rolls 112 and 113 is minimized. Applyingwater to roll 112 before composite 16 makes contact reduces thelikelihood that composite 16 will adhere to roll 112. Composite 16 andbelt 40 pass through the nip defined by embossing roll 112 and backuproll 113; and raised areas 122 of the embossing roll form correspondingdepressions in the composite. A cross section of an embossed composite18 as formed by this step is shown in FIG. 7 and a plan view in FIG. 8.

In accordance with our invention, we have found it advantageous tocontrol the surface speed of rotating drum 83 relative to that ofembossing roll 112 and backup roll 113 so that the surface speed of drum83 is about 98 to 99% of that of rolls 112 and 113 and preferably isabout 98.2%. Advantageously, this speed relation can be maintained bysetting speed control 85 so that its output rotational shaft speed is inthe range of 98 to 99% of its input rotational shaft speed which is thesame rotational speed as that of line shaft 48. With this speedrelationship, we have found that appropriate tension is produced incomposite 16 so that the composite does not become distorted either bybunching up which causes lateral expansion in the direction transverseto the direction of travel of the web or by stretching in the directionwhich is the same as the direction of travel of the web. As a result,production line throughput is greatly increased and product quality isalso improved.

After passing through the nip formed by rolls 112 and 113, embossedcomposite 18 is cooled to a low enough temperature that the embossedcomposite 18 can be stripped from silicone carrier belt 40. Preferably,this cooling operation is accomplished by immersing composite 18 andbelt 40 in a water bath 125. This step permits accurate temperaturecontrol during all seasons. In practicing the preferred embodiment ofour invention we have found it satisfactory to cool composite 18 toabout 80° to 90° F. (27° to 32° C.). Excess water is then removed fromthe web by a high velocity air knife 124; and the embossed web isstripped from carrier belt 40.

At this point the carrier belt 40 reverses direction. The embossed web,however, moves onto a conveyor belt 130 which carries it through apre-annealing station 132 which partially removes the strains impartedby laminating and embossing. After pre-annealing, the embossed web iscooled to about 100° to 110° F. (38° to 43° C.). It then enters a tilecutting station 140 where it is aligned and cut into tiles in registerwith the pattern printed on the web. Tile cutting station 140 comprisesa tile cutter 142, electric eyes 144, 145, and equipment responsive tosignals from the electric eyes for aligning the web in the transverseand longitudinal directions.

Specific apparatus for aligning embossed composite 18 will be apparentto those skilled in the art from the teaching of Barchi et al.'s U.S.Pat. No. 3,465,384, entitled "Apparatus for Registration of PlasticWeb", which is incorporated herein by reference. As disclosed in thatpatent, a plastic web 6 is fed on a conveyor belt 28 into a tile cutter36. Photocells 32, 34 are used to maintain the desired transverseposition of the plastic web by driving a reversible motor 128 thatcontrols the lateral position of conveyor 28. The photocells sense thelateral position of the plastic web by sensing a continuous longitudinalstripe 92 that is embossed in the plastic web at the same time as adesign is embossed in the remainder of the web. In like fashion in thepresent invention, electric eyes 144, 145 sense registration marks thatare printed on the web along with the printed design. Advantageouslythese registration marks can be the same as those used to align the webat the embossing station. Numerous closed loop feedback systems forcontrol of both lateral and longitudinal position of the web will beapparent.

The tiles are cut so that they are slightly oversize. They are thenannealed in an annealing oven 150 at an oven temperature of about 350°F. (177° C.) to shrink them to their proper size. Finally they arecooled to ambient temperature and packaged for shipment. Scrap from thetile cutting operation is fed to a granulator 160 and returned toblenders 20 for further use.

Suitable formulations for base web 10, release paper 62 and vinyl film92 are set forth in the above referenced '686 patent. Preferably thebase web is formed of a vinyl composition comprising a minor portion ofplasticized vinyl chloride polymer, and/or vinyl acetate copolymer,containing at least 80% vinyl chloride, uniformly mixed with a majorproportion of mineral filler, said minor portion constituting about 16to 25% by weight of the composition and said major portion constitutingabout 75 to 84% by weight of the composition.

The operating temperatures set forth above are preferred. Operatingranges for the case where the plastic base web and the plastic wearlayer are vinyl compositions are as follows. The plastic base web 10 isheated to an average temperature in the range of about 200° F. to 280°F. (93° C. to 138° C.) prior to transfer printing; the release paper 62is heated to an average temperature in the range of about 60° F. to 120°F. (16° C. to 49° C.) prior to transfer printing; and the vinyl wearlayer and the plastic base web are heated to an average temperature inthe range of about 270° F. to 310° F. (132° C. to 154° C.) duringlamination.

As will be apparent, many of the individual pieces of apparatus used inpracticing our invention are conventional. Extrusion equipment, heaters,printing stations, laminating stations, embossing stations, die cuttingequipment and aligning apparatus are old. However, the combination ofthis equipment to produce tile that is embossed in register with printon a continuous basis, at a high output rate and yielding a highpercentage of usable tile is new.

While the invention has been described in conjunction with specificembodiments, it is evident that numerous alternatives, modifications,and variations will be apparent to those skilled in the art in light ofthe forgoing description.

What is claimed is:
 1. A method of making, on a continuous basis, acomposite vinyl tile comprising the steps of:forming a continuous baseweb on a continuously moving supported surface traveling in asubstantially horizontal direction, said web being formed from a vinylcomposition, said moving surface being made of a material such that thebase web will adhere to the surface when the web is hot but can beremoved from it when the web is cooled, heating said base web,transferring a printed design from a pre-printed stable carrier sheet toa surface of the heated continuous base web, said printed design beingformed by a vinyl material compatible with said base web, said printeddesign including a first portion which constitutes a decorative designfor the composite vinyl tile and a second portion which providesregistration indicia for use in manufacturing thereof, laminating aclear plastic wear layer over the printed design on the base web, afterthe base web is laminated, aligning the web by means of the printedregistration indica so that the web is aligned with an embossing roll inboth a direction transverse to the direction of travel of the web and adirection that is the same as the direction of travel of the web,mechanically embossing the printed surface of the base web withdepressions in registration with the printed decorative design, afterthe base web is embossed, cooling the base web, stripping the cooled webfrom the moving surface, after stripping the base web from the movingsurface, aligning the web by means of the printed registration indiciaso that the web is aligned with a cutting tool in both the directiontransverse to the direction of travel of the web and the direction thatis the same as the direction of travel of the web, after aligning theweb, cutting the base web into discrete tiles so that the decorativedesign is in register with the edges of the tiles, and after cutting thebase web into discrete tiles, annealing the cut tiles, characterized bythe step of continuously controlling the speed of the continuouslymoving base web in the laminating step relative to the speed of thecontinuously moving base web in the embossing step in order to maintainproper web tension so that the web does not expand laterally in thedirection transverse to the direction of travel of the web or stretch inthe same direction as the direction of travel of the web.
 2. The methodof claim 1 further comprising the step of cooling the web with waterprior to mechanical embossing so that stretching of the web by theembossing roll will not occur.
 3. The method of claim 1 furthercomprising the steps of:pre-annealing the web after it has been strippedfrom the moving surface, and cooling the pre-annealed web before it iscut.
 4. The method of claim 1 wherein the tiles are cut oversized andare shrunken to their proper size during annealing.
 5. The method ofclaim 1 wherein the wear layer is applied to the base web by a rotatingdrum whose surface speed is less than that at which the base web isdriven during the embossing step.
 6. The method of claim 5 wherein thesurface speed of the rotating drum is approximately 98 to 99% of that atwhich the base web is driven during embossing.
 7. The method of claim 5wherein the surface speed of the rotating drum is approximately 98.2% ofthat at which the base web is driven during embossing.
 8. The method ofclaim 1 wherein said plastic base web is formed from a vinyl compositioncomprising a minor portion of plasticized vinyl chloride polymer, and/orvinyl acetate copolymer, containing at least 80% vinyl chloride,uniformly mixed with a major proportion of mineral filler, said minorportion constituting about 16 to 25% by weight of the composition andsaid major portion constituting about 75 to 84% by weight of thecomposition.